Simulation of the evolution of particle size distributions in a vehicle exhaust plume with unconfined dilution by ambient air

Over the past several years, numerous studies have linked ambient concentrations of particulate matter (PM) to adverse health effects, and more recent studies have identified PM size and surface area as important factors in determining the health effects of PM. This study contributes to a better understanding of the evolution of particle size distributions in exhaust plumes with unconfined dilution by ambient air. It combines computational fluid dynamics (CFD) with an aerosol dynamics model to examine the effects of different streamlines in an exhaust plume, ambient particle size distributions, and vehicle and wind speed on the particle size distribution in an exhaust plume. CFD was used to calculate the flow field and gas mixing for unconfined dilution of a vehicle exhaust plume, and the calculated dilution ratios were then used as input to the aerosol dynamics simulation. The results of the study show that vehicle speed affected the particle size distribution of an exhaust plume because increasing vehicle speed caused more rapid dilution and inhibited coagulation. Ambient particle size distributions had an effect on the smaller sized particles (approximately 10 nm range under some conditions) and larger sized particles (>2 microm) of the particle size distribution. The ambient air particle size distribution affects the larger sizes of the exhaust plume because vehicle exhaust typically contains few particles larger than 2 microm. Finally, the location of a streamline in the exhaust plume had little effect on the particle size distribution; the particle size distribution along any streamline at a distance x differed by less than 5% from the particle size distributions along any other streamline at distance x.     

Environmental and phylogenetic correlates of Eulemur behavior and ecology (Primates: Lemuridae)

The extent of diversity within closely related taxa may be a function of their shared evolutionary history or of selective forces causing adaptive changes. Examining variation among taxa within a single genus may help to identify flexibility in trait variation because recently diverged populations are more likely living in the environment of adaptation. This study examines correlates of diversity in Eulemur, a genus that has a wide distribution in a variety of habitat types throughout Madagascar. Previously published data were gathered from 11 long-term studies of Eulemur populations. Variables were categorized into multiple datasets: (1) environmental characteristics, (2) social organization, and (3) ecology, which included subsets for ranging behavior, diet, and activity budget. Molecular phylogenies from the literature were used to create the fourth and final dataset, a dissimilarity matrix of evolutionary distance among the 12 species and subspecies. Principal components and cluster analyses were implemented to examine the overall ecological similarity among Eulemur populations and to determine which variables contribute most to the variation among taxa. Partial Mantel tests were conducted to test for correlations among the dataset matrices. The results suggest ecological flexibility for the genus, in particular, populations in similar environments displayed similar activity patterns. In contrast, social organization showed no relationship with environment but was correlated with phylogenetic distance among populations. While Eulemur seems to demonstrate some flexibility for ecological adaptations, characteristics related to group size and sex ratio more closely track phylogeny and thus may be less flexible.Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible to authorized users.     

Giving respondents time to think in contingent valuation studies: A developing country application

This paper evaluates whether the time given people to think about their responses to CVM valuation questions influences their answers. Our study was conducted in Nigeria as part of an evaluation of rural households' willingness to pay for public taps and private connections to improved drinking water systems. Respondents who were allowed time to evaluate the proposed water system bid significantly less than those who did not have that time. Moreover, this conclusion was upheld regardless of whether the water system was a public tap or a private connection.     

Crash risk perception of sleepy driving and its comparisons with drink driving and speeding: Which behavior is perceived as the riskiest?

Objective: Driver sleepiness is a major crash risk factor but may be underrecognized as a risky driving behavior. Sleepy driving is usually rated as less of a road safety issue than more well-known risky driving behaviors, such as drink driving and speeding. The objective of this study was to compare perception of crash risk of sleepy driving, drink driving, and speeding.

Methods: Three hundred Australian drivers completed a questionnaire that assessed crash risk perceptions for sleepy driving, drink driving, and speeding. Additionally, the participants' perceptions of crash risk were assessed for 5 different contextual scenarios that included different levels of sleepiness (low, high), driving duration (short, long), and time of day/circadian influences (afternoon, nighttime) of driving.

Results: The analysis confirmed that sleepy driving was considered a risky driving behavior but not as risky as high levels of speeding (P < .05). Yet, the risk of crashing at 4 a.m. was considered as equally risky as low levels of speeding (10 km over the limit). The comparisons of the contextual scenarios revealed driving scenarios that would arguably be perceived as quite risky because time of day/circadian influences were not reported as high risk.

Conclusions: The results suggest a lack of awareness or appreciation of circadian rhythm functioning, particularly the descending phase of circadian rhythm that promotes increased sleepiness in the afternoon and during the early hours of the morning. Yet, the results suggested an appreciation of the danger associated with long-distance driving and driver sleepiness. Further efforts are required to improve the community's awareness of the impairing effects from sleepiness and, in particular, knowledge regarding the human circadian rhythm and the increased sleep propensity during the circadian nadir.     

Isolines as a new tool to assess the energy costs of the production and distribution of multiple sources of seafood

Consumer-based ocean conservation efforts focus attention on seafood that is produced in an “eco-friendly” manner. However, many species can be produced either in aquaculture operations or harvested within wild capture fisheries, and each mode of production differs in their environmental impacts as well as their energy requirements. Complicating the assessment of eco-friendly seafood is the fact that seafood is a global commodity, the suppliers of which utilize a variety of methods to distribute the product from producer to consumer (e.g. ship, truck, airplane). Like the modes of production, these various modes of distribution differ in their energy intensity. This analysis assesses the overall energy requirements of production and distribution (E_P&D) of seafood to evaluate how the energy costs of distribution influence the total energy cost of seafood produced by different methods. This paper develops the concept of energy isolines as a tool to assess E_P&D. Isolines are a graphical method to succinctly integrate multiple distance assessments so that the best sourcing option can be determined. The isolines are then used to assess how the energy cost of distribution functions as a component of the overall energy cost, and how this influences the E_P&D of a product originating from two different sources with inherently different energy costs of production. Using scallops and salmon as examples, this analysis has revealed that an “eco-friendly” seafood commodity (one produced with less energy) produced far from its destination market could have a higher total E_P&D compared to a local, less “eco-friendly” product (that takes more energy to produce). Finally, this paper evaluates strategies to minimize the overall E_P&D of seafood. Overall, further work on energy audits of seafood focused the need to maintain a global perspective to determine seafood with the lowest overall energy cost of production and distribution.     

Practical actions for applied systematic conservation planning

Systematic conservation planning is intended to inform spatially explicit decision making. Doing so requires that it be integrated into complex regulatory and governance processes, and there are limited instances where this has been achieved effectively. South Africa is a global leader in the application of conservation plans, the outputs of which are widely used for spatial planning and decision making in many spheres of government. We aimed to determine how conservation planning in the country progressed from theory to implementation, and to identify practical actions that enabled this transition, by assessing temporal trends in the characteristics of conservation plans (1990–2017, n = 94). Since 2010 conservation planning has entered an operational period characterized by government leadership of plans, administrative rather than ecological planning domains, decreasing size of planning units, increasing emphasis on end-user products, and scheduled revision of plans. Key actions that enabled this progression include transitioning leadership of plans from scientists to practitioners, building capacity within implementing agencies, creating opportunities to integrate plans in legislative processes, establishing a strong community of practice, adopting implementation-focused methods, and balancing standardization with innovation. Learning from this model will allow other countries, particularly those with a similar megadiverse, developing context, to operationalize conservation planning into spatial planning and decision making.     

JEEM and Non-market Valuation: 1974–1998

This paper considers whether the Journal of Environmental Economics and Management (JEEM) has had impact on the development and applications of the methods used to estimate economic values for non-marketed environmental resources. Journal editors control the research dialogue in a discipline and as a result have the potential to influence its scope and direction. At least four areas of research have been influenced by JEEM, the theory and practice of contingent valuation, the use of preference restrictions in valuation, the development and application of corner solution models, and the role of substitution between environmental resources for valuation.     

Uncertainty and allocation decisions involving unique environmental resources

The implications of the treatment of uncertainty in the definition of optimal investment criteria for irreversible allocations of unique environmental resources are considered herein. This analysis argues that the single-project, orientation of conventional cost-benefit analysis can lead to inconsistent decisions because it fails to take account of the potential for risk pooling across projects. In the models discussed in this paper uncertainty arises because the planner must estimate the net benefits associated with a mix of developed and preserved natural environments. The results suggest that the criteria for optimal investment plans will be affected by those factors influencing this uncertainty. Both the scale and timing of optimal investments may be altered from those prescribed with the conventional (Fisher-Krutilla-Cicchetti rule) framework when the potential for risk pooling is introduced. Thus, it is important to consider as a part of the specification of the objective function the factors which give rise to uncertainty.     

Clogging of finger drain systems in MSW landfills

A numerical model ‘BioClog’ is used to examine clogging of granular drainage material within finger drains at the base of landfills. The reduction in porosity of drainage material is evaluated as the accumulation of clog mass reduces the pore spaces of granular media. The leachate mounding within the landfills caused by the reduction in hydraulic conductivity of finger drain is modeled. The effect of overburden pressure on the engineering properties of waste material and consequent leachate mounding is considered. The calculated rates of leachate mound development for two landfills with finger drain leachate collection are shown to be in encouraging agreement with the observed data at the times when data were available. It is demonstrated that a significant leachate mound can be expected to develop over time when the leachate collection system is comprised of finger drains; however the rate of increase and the magnitude at a given time will depend on a number of factors including the grainsize, thickness and spacing of the finger drains, and the thickness of waste as well as the leachate generation rate.